In display spaces such as museums and show windows, many hooks hanging exhibits such as paintings and commodities have been used. In addition, hooks attached with a wire grip that can place the hook at an arbitrary position (height) of the hanging wire have been also used frequently.
The present inventor has developed various kinds of such hooks attached with a wire grip (for example, see Patent document 1) and has also manufactured and sold safety hooks disclosed in FIG. 7 of Patent document 2, etc.